For me Fossamail does not usually add quotes around the sender. I have seen it rarely but suspect it is something to do with the sender's email provider or client.LATER:A Duckduckgo search for "email quotes around sender" suggests that this has been noticed in Thunderbird for years and various explanations have been offered for the cause. Here is one:https://support.mozilla.org/en-US/questions/1060627

I looked up in my FM 25.2.1 and can't find those quotes anywhere, except in a send field of one single mail (and for one other Recipient in the mail List View).My first guess was it's perhaps a mark, if the sender isn't in the adress book, but this was wrong.

I don't think this thing is related to any add-on, since I'm using 4 different email accounts in FossaMail right now, and only the Gmail account is the one with quotation marks. But I'm beginning to think that this was an issue with Gmail, because I added an email account —not Gmail's— to FossaMail yesterday and no quotes is displayed in the Sender field.

So, after all, I think this "suggestion" is not valid since it's no related to FossaMail actually.